Introduction
This invention is concerned in general with silver catalysts, their manufacture and their use in the manufacture of ethylene oxide in commercial concentrations in the presence of a gas phase inhibitor, especially a gas phase chloride inhibitor, and advantageously carbon dioxide recycle. The catalyst of this invention comprises a supported silver catalyst. The catalyst contains cesium salts of an oxyanion in combination with at least one other alkali metal and/or alkaline earth metal salt of a halide or an oxyanion. Preferably, another alkali metal is present and is lithium, sodium, potassium and/or rubidium. The oxyanions contain elements other than the oxygen therein having an atomic number of 7 or 15 to 83, inclusive, and being from the groups 3b, through 7b, inclusive, and 3a through 7a, inclusive, of the Periodic Table of the Elements. Thus, the catalyst, when utilized in the manufacture of ethylene oxide, contains a select class of salts of cesium with one or more other select classes of salts of other alkali metals (excluding francium) and alkaline earth metals. The amount of these salts employed is not governed by prior art notions of weight or volume percentages because, as will be explained herein, such factors cease in general to be relevant. Thus, this invention allows the use of amounts of alkali metals and alkaline earth metals which cover a broad range to yield catalysts having desirable performances.